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Sniff test
Last words past and present at newscientist.com/lastword
THE LAST WORD Explosive power Last night, my wife and I were awoken by two loud cracks a second or so apart. The day after, I discovered that the 9-volt battery cell I’d removed from a fire alarm the night before appeared to have exploded (see photo). What might have caused this in a depleted cell, and why two cracks?
n This photo shows a “battery” in the real sense, being constructed of six 1.5-volt cells connected in series. Some batteries have stacked flat cells but others, like the one pictured, have a three-bytwo array of cylinder cells. Because the battery’s terminals are at the same end, a circuit can easily be completed if they come into contact with a metal object – if stored in a metal box, say. The battery has an internal resistance, and heats up when a current flows through it. This causes the water in its electrolyte to vaporise and increase the internal pressure, then… bang! The first crack would have been the electron-collecting pin being fired from a cell like a bullet from a gun. The second would have been a failure in the casing of the adjacent cell, causing it to be ejected from the battery. Even a partially depleted battery can supply enough current to heat the metal contacts and internal parts, and also any metal that the battery terminals may touch – and perhaps start a fire. There have been serious injuries to sensitive parts when 9-volt batteries have come into contact
The writers of answers that are published in the magazine will receive a cheque for £25 (or US$ equivalent). Answers should be concise. We reserve the right to edit items for clarity and style. Please include a daytime telephone number and an email address if you have one. New Scientist retains total editorial control over the published content. Reed Business Information Ltd reserves all rights to reuse all question and answer material that has been
with coins in trouser pockets, completing a short circuit. David Muir Science Department Portobello High School Edinburgh, UK
Cold calling Vaccination against flu viruses is well established and reasonably successful, especially in high-risk groups such as the very young and elderly. Colds are also caused by viruses and, although they are less virulent, they occur more frequently, making the sum total of sickness and workdays lost comparable. Why is there no vaccination programme for the common cold?
n The lack of a vaccination for the common cold is not for want of trying. Research into both prevention and cure demonstrates how intractable the problem can be, but the matter has become more urgent now that colds have been
submitted by readers in any medium or in any format and at any time in the future. Send questions and answers to The Last Word, New Scientist, 110 High Holborn, London WC1V 6EU, UK, by email to [email protected] or visit www.newscientist.com/topic/lastword (please include a postal address in order to receive payment for answers). Unanswered questions can also be found at this URL.
implicated as a cause of asthma. Smallpox, polio and influenza, which have been countered by vaccination, are caused by a finite number of viruses. The common cold, in contrast, is merely a catch-all term for a wide range of opportunist infections of the upper respiratory tract. Colds are usually ascribed to rhinoviruses, which were discovered as causative agents in 1956. However, work at Cardiff University – which has a dedicated common cold research centre – suggests that perhaps only 30 per cent of colds are caused by these viruses. The other culprits can be coronaviruses and adenoviruses, and some colds may in fact be mild attacks of influenza. As for rhinoviruses themselves, it is usually stated that there are 99 strains, but the UK National Health Service suggests there are 138 recognised serotypes – and there must be many more waiting to be examined. Each would require its own vaccine. Furthermore, these small strands of RNA both mutate and exchange genetic information, so there will always be novel strains to deal with. Collectively, cold viruses are among nature’s great success stories. A clever pathogen does not destroy its host or immobilise a person to the extent that they cannot walk around and spread their infection. Colds are annoying, and a drain on the economy, but are not seen as enough of a threat to attract the funding given to heart disease and
cancer research; nor are they scary enough to make people modify their behaviour to any great extent. Because they are not taken as seriously as, say, Ebola and H5N1 influenza, colds are the great survivors. Christine Warman Hinderwell, North Yorkshire, UK
This week’s questions Fritillary flitter
What causes butterflies to flutter and flit up and down in the charming way they do? Dermot Barrett Kingston, Ontario, Canada A chill wind
Objects that enter Earth’s atmosphere are subject to extreme heat through air friction – so much so that returning spacecraft have to be very well insulated, and rocks and small asteroids burn up. How fast would I have to go to feel heat from air friction? When I’m on my bike going downhill quickly, I can only feel it getting colder and colder. Ben Cordle London, UK Sniff test
If a dog’s sense of smell is thousands of times more sensitive than ours, why do they have to get so close to smell each other’s bottoms? Jay Brookhiemer London, UK
Question Everything The latest book of science questions: unpredictable and entertaining. Expect the unexpected Available from booksellers and at newscientist.com/questioneverything
THE LAST WORD Explosive power Last night, my wife and I were awoken by two loud cracks a second or so apart. The day after, I discovered that the 9-volt battery cell I’d removed from a fire alarm the night before appeared to have exploded (see photo). What might have caused this in a depleted cell, and why two cracks?
n This photo shows a “battery” in the real sense, being constructed of six 1.5-volt cells connected in series. Some batteries have stacked flat cells but others, like the one pictured, have a three-bytwo array of cylinder cells. Because the battery’s terminals are at the same end, a circuit can easily be completed if they come into contact with a metal object – if stored in a metal box, say. The battery has an internal resistance, and heats up when a current flows through it. This causes the water in its electrolyte to vaporise and increase the internal pressure, then… bang! The first crack would have been the electron-collecting pin being fired from a cell like a bullet from a gun. The second would have been a failure in the casing of the adjacent cell, causing it to be ejected from the battery. Even a partially depleted battery can supply enough current to heat the metal contacts and internal parts, and also any metal that the battery terminals may touch – and perhaps start a fire. There have been serious injuries to sensitive parts when 9-volt batteries have come into contact
The writers of answers that are published in the magazine will receive a cheque for £25 (or US$ equivalent). Answers should be concise. We reserve the right to edit items for clarity and style. Please include a daytime telephone number and an email address if you have one. New Scientist retains total editorial control over the published content. Reed Business Information Ltd reserves all rights to reuse all question and answer material that has been
with coins in trouser pockets, completing a short circuit. David Muir Science Department Portobello High School Edinburgh, UK
Cold calling Vaccination against flu viruses is well established and reasonably successful, especially in high-risk groups such as the very young and elderly. Colds are also caused by viruses and, although they are less virulent, they occur more frequently, making the sum total of sickness and workdays lost comparable. Why is there no vaccination programme for the common cold?
n The lack of a vaccination for the common cold is not for want of trying. Research into both prevention and cure demonstrates how intractable the problem can be, but the matter has become more urgent now that colds have been
submitted by readers in any medium or in any format and at any time in the future. Send questions and answers to The Last Word, New Scientist, 110 High Holborn, London WC1V 6EU, UK, by email to [email protected] or visit www.newscientist.com/topic/lastword (please include a postal address in order to receive payment for answers). Unanswered questions can also be found at this URL.
implicated as a cause of asthma. Smallpox, polio and influenza, which have been countered by vaccination, are caused by a finite number of viruses. The common cold, in contrast, is merely a catch-all term for a wide range of opportunist infections of the upper respiratory tract. Colds are usually ascribed to rhinoviruses, which were discovered as causative agents in 1956. However, work at Cardiff University – which has a dedicated common cold research centre – suggests that perhaps only 30 per cent of colds are caused by these viruses. The other culprits can be coronaviruses and adenoviruses, and some colds may in fact be mild attacks of influenza. As for rhinoviruses themselves, it is usually stated that there are 99 strains, but the UK National Health Service suggests there are 138 recognised serotypes – and there must be many more waiting to be examined. Each would require its own vaccine. Furthermore, these small strands of RNA both mutate and exchange genetic information, so there will always be novel strains to deal with. Collectively, cold viruses are among nature’s great success stories. A clever pathogen does not destroy its host or immobilise a person to the extent that they cannot walk around and spread their infection. Colds are annoying, and a drain on the economy, but are not seen as enough of a threat to attract the funding given to heart disease and
cancer research; nor are they scary enough to make people modify their behaviour to any great extent. Because they are not taken as seriously as, say, Ebola and H5N1 influenza, colds are the great survivors. Christine Warman Hinderwell, North Yorkshire, UK
This week’s questions Fritillary flitter
What causes butterflies to flutter and flit up and down in the charming way they do? Dermot Barrett Kingston, Ontario, Canada A chill wind
Objects that enter Earth’s atmosphere are subject to extreme heat through air friction – so much so that returning spacecraft have to be very well insulated, and rocks and small asteroids burn up. How fast would I have to go to feel heat from air friction? When I’m on my bike going downhill quickly, I can only feel it getting colder and colder. Ben Cordle London, UK Sniff test
If a dog’s sense of smell is thousands of times more sensitive than ours, why do they have to get so close to smell each other’s bottoms? Jay Brookhiemer London, UK
Question Everything The latest book of science questions: unpredictable and entertaining. Expect the unexpected Available from booksellers and at newscientist.com/questioneverything